1. Field of Invention
The present invention relates to a ground fault circuit interrupter, and more particularly to an always-open trip breaker used in a ground fault circuit interrupter with a programmable integrated module and an End-of-life termination function.
2. Description of Related Arts
When the hot wire or neutral wire is short circuited to the ground, the ground fault circuit interrupter is used as an electrical switch not only for protecting the electrical circuit of the electrical appliance from being damaged caused by overload or short circuiting but also for preventing the user from being electric shocked. The ground fault circuit interrupter has a higher sensitivity and faster response in comparison with other protection devices, such as fuse or automatic switch. The ground fault circuit interrupter can rapidly cut off the current and prevent current overload.
Accordingly, the automatic switch or the fuse has an operation value corresponding to the normal operation current in order to withstand the operation current passing through. Once the fault current is larger than the operation value, the automatic switch or the fuse will cut off the electrical connection between the load and the power supply. On the other hand, the leakage protector use the residual current produced in the ground fault to cut off the power supply. Therefore, the operation value of the leakage protector is relatively small (generally set as 6 milliampere). However, when the current is leaked by human contact or to the outer casing, the residual current will substantially increase. It is worth mentioning that the ground fault circuit interrupter can determine and stop the residual current so as to cut off the current from the power supply.
Generally speaking, the ground fault circuit interrupter comprises a trigging mechanism to rapidly cut off the current to the electrical appliance, wherein there are two different types of tripping mechanisms being commonly used. The first type is the “always-close” type tripping mechanism electrically connecting to the movable terminal and the fixed terminal for electrical connection. The mechanical pressure between the movable terminal and the fixed terminal relies on the trip breaker of the tripping mechanism implemented using a solenoid or electromagnet force. The advantage of such “always-close” tripping mechanism is that the operation is reliable, the circuit and the mechanism is simple. However, the drawback of such “always-close” type tripping mechanism is that the coil of the trip breaker consumes part of the electrical power. Another type is the “always-open” type tripping mechanism relying on an impulsive current to the coil of the trip breaker such that the trip breaker shifts at an off-balance state by means of the electromagnetic force to electrically connect with the movable terminal and the fixed terminal. Accordingly, a locker is incorporated with the trip breaker to provide a mechanical pressure between the movable terminal and the fixed terminal. Such “always-open” tripping mechanism requires the locker and a logic circuit to incorporate with the trip breaker, such that the “always-open” tripping mechanism has relatively complicated electrical and mechanical configurations. However, the “always-open” tripping mechanism does not require any current passing through the coil thereof for operation. In other words, the “always-open” tripping mechanism does not normally consume any electrical power. Comparing with the two different types of tripping mechanisms, the “always-close” tripping mechanism is commonly used for the simple IC circuit product because the “always-close” tripping mechanism has simplified electrical and mechanical configurations.
The ground fault circuit interrupter generally comprises a fault current induction mechanism, including a sensor coil and a driver coil, a signal rectifying circuit, a signal amplifying circuit, a signal comparing circuit, a threshold switch circuit, an operation mechanism, and other peripheral circuits. Accordingly, a signal induction mechanism comprises two zero-phase current inductors, wherein one of the current inductors has a coil ratio of primary and secondary windings being set as 1:1000 while another current inductor has a coil ratio of primary and secondary windings being set as 1:200. The signal rectifying circuit is coupled with capacitors and resistors to form a signal extraction circuit, wherein the signal amplifying circuit and the signal comparing circuit are combined to form a semiconductor chip such as LM1851 chip from National and RV4145A chip from Fairchild. The threshold switch circuit comprises a silicon controlled rectifier (SCR). The operation mechanism comprises a trip breaker and its corresponding components thereof, and peripheral circuit and components comprising a movable terminal, a fixed terminal, a test button, and a reset button. Before the standard of UL943-2006 is set, the function of the ground fault circuit interrupter is that: (1) when the hot wire and neutral wire is faulty to the ground, and the fault current is bigger than 6 mA, the power supply is cut off; (2) when there is no fault current or the fault current is not larger than the threshold, the ground fault circuit interrupter can be reset by the reset button to re-connect the ground fault circuit interrupter with the power supply; (3) the test button is used for testing the function of the ground fault circuit interrupter by pressing the test button to cut off the power supply; (4) when the wires at the load and the power supply are reversely connected, the ground fault circuit interrupter cannot be electrified so as to protect the load in responsive to the improper connection.
According to the standard before UL943-2006, the ground fault circuit interrupter does not have the End-of-life automatic self-checking function. The user manually presses the test button to check whether the ground fault circuit interrupter is faulty or failed. The trip breaker must be operated with the constant power supply, which will shorten the service life of the trip breaker. Thus, there is no indicating signal, such as sound signal or light signal, to indicate the operating status of the trip breaker.
Along with the programmable integrated module application, it is possible to incorporate the programmable integrated module with the “always-open” tripping mechanism with the logical control.
The present invention provides a programmable integrated module and a control switch incorporating with the “always-open” tripping mechanism to cut off the current exceeding the breaker rating and to protect the wrong wiring connection of the circuit.